The present invention relates to an arrangement for determining the location relative to eyeglass frames of points at which visual axes penetrate through eyeglass areas of eyeglasses.
It is a current practice to select the size of eyeglass frames, after the customer has chosen the style, in accordance with the head measurements of the particular customer, such as the head width or temple-to-temple distance, and/or the shape and size of the nose of the customer. While the distance between the eyes of the respective customer may be taken into consideration by the optician when recommending, or by the customer when choosing, the style of the eyeglass frame, it plays no role, or only a subordinate one, in selecting the size of the eyglass frame for the particular customer. Hence, the positions of the eyes relative to the eyeglass areas (that is the areas which are eventually occupied by the corrective lenses) usually vary from customer to customer, and so do the points of penetration of the optical axes through these eyeglass areas. In addition thereto, the positions of the eyes and thus the locations of the points of penetration of the optical axes of the eyes with the eyeglass areas depend on the distance between the object being observed and the user of the eyeglasses.
It is very desirable that the optical axes of the corrective lenses coincide with the visual axes of the eyes. In order to be able to achieve this, it is necessary to ascertain the locations at which the visual axes of the two eyes penetrate through the eyeglass areas of the eyeglass frame. As explained above, these locations are different for reading glasses and for distant vision glasses.